Technical data

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3.0 Appliance Operation
© Baxi Heating UK Ltd 2007
3.1 Operating Mode (Fig. 2)
1. With a demand for heating, the pump circulates water
through the primary circuit. At a pre-determined flow rate
the hydraulic differential pressure switch operates, initiating
the ignition sequence.
2. The main burner ignites at low rate, then the gas valve
controls the gas rate to maintain the heating temperature
measured by the temperature sensor.
3. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the burner
relights automatically (anti-cycling). The pump continues to
run during this period.
4. When the demand is satisfied the burner is extinguished
and the pump continues to run for a period of 3 minutes
(Pump Overrun).
IMPORTANT: When the selector switch is in the ‘0’
(Off) position the electrical supply to the boiler is
isolated. The boiler will not operate.
3.2 Frost Protection Mode
1. The frost protection mode is integral to the appliance and
functions when the selector switch (see Section 2.1) is in the
ON position ( ). If the system temperature falls below
5° C then the boiler will fire on its minimum setting until a
flow temperature of 30° C is reached. Further protection
can be incorporated by using a system frost thermostat.
3.3 Pump Protection
1. With the selector switch (see Section 2.1) in the ON
position ( ) the pump will automatically operate for 1
minute in every 24 hours to prevent sticking.
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3
Key
1 Heat Exchanger
2 Burner
3 Ignition Electrode
4 Flame Sensing Electrode
5 Gas Valve
6 Pump
7 Automatic Air Vent
8 Pressure Relief Valve
9 Boiler Drain Point
10 Gas Inlet
11 Boiler Flow
12 Boiler Return
13 Pressure Gauge
14 Automatic By-Pass
15 Hydraulic Differential Pressure Sensor
16 Safety Thermostat
17 Temperature Sensor
18 Expansion Vessel
19 Temperature Sensor
20 Secondary Heat Exchanger
Boiler Primary Circuit
Fig. 2
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